At 02:26 PM 1/16/98 -0900, you wrote:
>I have heard that for a period of time every day (anywhere from 15 minutes
>up to an hour), the military completely scrambles the GPS system, and that
>during this period, your GPS readings are off by a considerable amount.
>
Hi, Andrew Sorensen and all interested,

I got myself a Magellan 3000 XL for Christmas. The instruction manual says
that the Department of Defense has introduced errors into the satellite
signals for security reasons. These errors are referred to as Selective
Availability - that may well be what you mention. And I quote from the book:

"At present, your GPS position will be accurate to within 100 meters
horizontally and 150 meters vertically. Your horizontal coordinates may be
slightly more than 100 meters from your actual position about 5% of the
time, due to the errors introduced by Selective Availability. Elevation
may vary even more."

Since I am a complete neophyte at using a GPS, I cannot comment on this
error, I can only be aware that it does, indeed, exist.

Regards, Diann MacRae
Bothell, tvulture at halcyon.com